L85 Never too old to learn
It is + adj. / done / n. + 主语从句
It is adj. + 主语从句
It is obvious that he was very embarrassed.
It is done + 主语从句（句式中有it is ...that，不要判断为宾语从句。宾从不用形式主语）
It is said that if anyone touches the tree, he will have bad luck; if he picks a leaf, he will die.
It is n. + 主语从句
It is a curious coincidence that the day before his retirement, Mr. Page will have been teaching for a total of forty years.